1. Field of the Invention
The present disclosure relates to a magnetic switch.
2. Background of the Invention
A magnet switch is a device used for switching (opening or closing) power of an electric line, and is extensively utilized for industrial, household, and vehicle purposes. In particular, a magnetic switch for a vehicle is used to supply and cut off DC power provided from a storage battery of a vehicle such as a hybrid vehicle, a fuel cell vehicle, or a golf cart.
Such a magnetic switch is closed and a current flows when a stationary contact arm and a movable contact arm are brought into contact with each other, and in particular, in order to control an arc generated when DC power having a high voltage is cut off, a permanent magnet is used. The magnetic switch employs a breaking mechanism in which a permanent magnet is appropriately disposed in the vicinity of a stationary contact arm and a movable contact arm where an arc is generated, and an arc is controlled and cooled to be extinguished using a force determined according to strength and a direction of magnetic flux generated in the permanent magnet, a current direction, and an elongated length of an arc. Here, an arc extinguishing unit and a motor magnet may be damaged by the generated arc, and thus, in order to enhance operational reliability of a magnetic switch, it is required to extinguish the arc and protect the magnetic switch against the arc. The present invention provides enhancement of operational reliability of a high voltage DC switch, and the foregoing requirements are satisfied by using a protecting device formed of a resin material.
FIG. 2 is a view illustrating a related art magnetic switch 100. As illustrated in FIG. 2, the related art magnetic switch includes a moving unit 140 movable with a contact, a gas sealing unit for hermetically sealing an arc-extinguishing gas filling space for arc extinguishment, and a magnetic driving unit providing driving force to drive the moving unit 140. Here, the moving unit includes a shaft 141, a cylindrical movable core 145 connected to a lower portion of the shaft 141 such that the cylindrical movable core 145 can be linearly movable together with the shaft 141, and disposed to be movable linearly by a magnetic pull from the magnetic driving unit, and a movable contact arm 150 connected to an upper end portion of the shaft 141 to form an electrical contact portion. A fixed core 143 is provided in a position facing the movable core 145 and surrounds the shaft 141, and the fixed core 143, the movable core 145, the second barrier 118, and the like, form a circuit providing a path along which magnetic flux moves.
The gas sealing unit is provided in the vicinity of an upper portion of the moving unit to form an arc extinguishing gas chamber in which an arc extinguishing gas of the magnetic switch is airtightly installed (or sealed), and includes a tubular insulating member, a pair of fixed electrodes 121 penetrating through the insulating member to connect the interior and exterior of the insulating member and airtightly coupled to the insulating member, a tubular airtight member provided between the insulating member and a second barrier 118 (to be described hereinafter) to airtightly seal the insulating member and the second barrier 18 and having a step, and a cylinder 160 formed of a non-magnetic material and installed to airtightly surround the movable core 145 and the fixed core 143. Here, a DC power source side and a load side are connected to the pair of fixed electrodes 121 electrically, for example, through an electric line.
The magnetic driving unit for switching the magnetic switch by driving the movable core 145 and the movable contact arm 150 (to be described hereinafter) by generating a magnetic pull includes a magnetizing coil 131 and the second barrier 118. Here, the magnetizing coil 131 is a driving coil provided in a lower portion of the magnetic switch. When a current is applied, the magnetizing coil 131 is magnetized, and when an application of a current is cut off, the magnetizing coil is demagnetized. The magnetizing coil 131 provides driving force to the moving unit for switching (or opening and closing) a contact by generating a magnetic pull in the magnetic switch. The second barrier 118 is installed above the magnetic coil 133, and when the magnetic coil 133 is magnetized, the second barrier 118 forms part of a movement path of magnetic flux, together with the movable core 145 and the fixed core 143. When the magnetic coil 133 is magnetized, a lower yoke forms a movement path of magnetic flux, together with the second barrier 118, the movable core 145, and the fixed core 143.
In FIG. 2, a bobbin 131 may allow the magnetizing coil 133 to be wound therearound, and supports the magnetizing coil 133. A return spring 183 is installed above the shaft 141, and when the magnetizing coil 133 is demagnetized, the return spring 183 provides elastic force to return the movable core 145 to the original position, that is, to a position spaced apart from the fixed core 143. In FIG. 2, a contact spring is a spring for maintaining contact pressure between contacts when the movable contact arm 150 is in an ON position of the magnetic switch in which the movable contact arm 150 is in contact with the fixed electrode 121. In FIG. 1, a housing 110 accommodates the magnetic switch according to the related art.
An operation of the magnetic switch according to the related art configured as described above will be described. When the magnetizing coil 133 is magnetized upon receiving a current, magnetic flux generated by the magnetic coil 133 may move along a movement path of the magnetic flux formed in the movable core 145, the fixed core 143, the second barrier 118, and the lower yoke (not shown), forming a closed circuit of magnetic flux, and at this time, the movable core 145 linearly moves to be brought into contact with the fixed core 143, and at the same time, the shaft 141 connected to be moved together with the movable core 145 moves upwardly. Then, the movable contact arm 150 installed in eh upper end portion of the shaft 141 is brought into contact with the fixed electrode 121 and the DC power source side and the load side are connected to enter an ON state in which DC power is supplied.
When a current supplied to the magnetizing coil 133 is cut off, the magnetizing coil 133 is demagnetized, and as the magnetizing coil 133 is demagnetized, the movable core 145 is returned to the original position spaced apart from the fixed core 143, by the return spring 183. Accordingly, the shaft 141 connected to be moved together with the movable core 145 moves downwardly. Then, the movable contact arm 150 installed in the upper end portion of the shaft 141 is separated from the fixed electrode 121, entering an OFF state in which the DC power source side and the load side are separated and supply of the DC power is cut off.
When power is applied through a coil terminal, magnetic force is formed in a coil assembly and the movable core 145 moves to push up the shaft in a direction toward the fixed core. Here, short-circuit performance (operational performance) of the magnetic switch is determined by compressive force of the two types of springs when the magnetic switch is turned on, and, in general, since a load of the contact spring 181 is considerably large, compared with the return spring 183, short-circuit performance of the magnetic switch relies on maximum compressive force of the contact spring. Compressive force of a spring is proportional to a maximum compression distance, and is determined by a distance between the fixed core and the movable core 145 and a distance between the fixed contact arm and the movable contact arm.
In general, short-circuit performance according to current capacity of a magnetic switch is determined according to maximum compressive force of the contact spring 181. In the related art, maximum compressive force of a spring is proportional to a compression distance of the spring, it is not easy to enhance compressive force of the spring in a limited space such as in the related art.